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Tropical Wave 04 Forecast To Bring Increased Cloudiness, Showers Into Weekend

May 25, 2023
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To date, three early-season tropical waves have moved south of Trinidad and Tobago, producing no measurable rainfall across the country. However, the fourth tropical wave, which is also the first analyzed by the National Hurricane Center, is forecast to change that on Friday into the weekend.

What you need to know

— Rainfall: Over the next five days, rainfall accumulations will vary between 10 and 55 millimeters across both islands. Isolated totals exceeding 50 millimeters are possible across eastern and southern areas of Trinidad, eastern Tobago, and western coastal Trinidad. In highly isolated areas, totals could exceed 100 millimeters over the five-day period in the above-mentioned areas. The heaviest rainfall days are expected on Saturday and Sunday as a result of Tropical Wave 04’s passage.
— Saharan Dust: Little to no Saharan Dust is forecast across Trinidad and Tobago over the next five days.
— Hazards: The main hazards, particularly on Saturday and Sunday, will be street/flash flooding and gusty winds. Though overall winds are forecast to remain near calm or light, in heavy showers or thunderstorms, wind gusts may exceed 45 KM/H. Daily through the next five days, localized street flooding is possible.
— Marine: Seas are forecast to be slight to moderate in open waters, with waves up to 1.5 meters and below 1.0 in sheltered areas. By Monday, seas are forecast to become slight, with waves in open waters reaching up to 1.25 meters. Seas may become locally choppy or rough in heavy showers or thunderstorms.

Latest Alerts

Trinidad and Tobago is NOT under any tropical storm or hurricane threat, watch, or warning at this time.

The Forecast

Friday

Friday
6 10 0 1
Mostly warm and humid after midnight with increasing cloudiness. Isolated to scattered showers and isolated thunderstorms are possible from the pre-dawn hours (4 AM) onwards, favoring eastern Trinidad and Tobago, gradually moving west. From daybreak, partly cloudy skies with isolated showers are possible, with increasing cloudiness and rainfall mainly after midday through the afternoon. Isolated heavy showers and thunderstorms are possible, favoring eastern areas of both islands, as well as isolated areas of western coastal Trinidad during the afternoon. A variably cloudy evening and night with isolated showers and offshore thunderstorms possible. Gusty winds, street/flash flooding possible.
Mostly warm and humid after midnight with increasing cloudiness. Isolated to scattered showers and isolated thunderstorms are possible from the pre-dawn hours (4 AM) onwards, favoring eastern Trinidad and Tobago, gradually moving west. From daybreak, partly cloudy skies with isolated showers are possible, with increasing cloudiness and rainfall mainly after midday through the afternoon. Isolated heavy showers and thunderstorms are possible, favoring eastern areas of both islands, as well as isolated areas of western coastal Trinidad during the afternoon. A variably cloudy evening and night with isolated showers and offshore thunderstorms possible. Gusty winds, street/flash flooding possible.
6/10
Thunderstorm Chances
Medium – High

Saturday

Saturday
6 10 0 1
Mostly cloudy with periods of showers, isolated thunderstorms, and rain across both islands after midnight and continuing through the day. Peak thunderstorm activity is forecast during the late morning through the afternoon across Trinidad. Conditions to settle by the evening but isolated showers and thunderstorms are possible nearing midnight, favoring eastern areas initially. Gusty winds, street/flash flooding possible.
Mostly cloudy with periods of showers, isolated thunderstorms, and rain across both islands after midnight and continuing through the day. Peak thunderstorm activity is forecast during the late morning through the afternoon across Trinidad. Conditions to settle by the evening but isolated showers and thunderstorms are possible nearing midnight, favoring eastern areas initially. Gusty winds, street/flash flooding possible.
6/10
Thunderstorm Chances
Medium – High

Sunday

Sunday
6 10 0 1
Isolated to scattered showers and isolated thunderstorms are forecast after midnight through daybreak, gradually settling, leading to a mostly cloudy day. However, by the late morning through the afternoon, isolated showers, with some becoming heavy, with isolated thunderstorms are forecast across mainly Trinidad, beginning in southeastern and western coastal areas. Conditions are forecast to settle by the evening, barring the odd shower. Isolated, offshore, nighttime thunderstorms are possible in the Gulf of Paria and east of T&T. Gusty winds, street/flash flooding possible.
Isolated to scattered showers and isolated thunderstorms are forecast after midnight through daybreak, gradually settling, leading to a mostly cloudy day. However, by the late morning through the afternoon, isolated showers, with some becoming heavy, with isolated thunderstorms are forecast across mainly Trinidad, beginning in southeastern and western coastal areas. Conditions are forecast to settle by the evening, barring the odd shower. Isolated, offshore, nighttime thunderstorms are possible in the Gulf of Paria and east of T&T. Gusty winds, street/flash flooding possible.
6/10
Thunderstorm Chances
Medium – High

Monday

Monday
4 10 0 1
Partly to mostly cloudy with isolated showers and isolated thunderstorms favoring the southern half of Trinidad from the early morning, with additional shower/thunderstorm development possible along western coastal Trinidad during the late morning through the afternoon. Elsewhere, partly to mostly cloudy with isolated showers/light to moderate rain. These conditions are forecast to continue into the night. Gusty winds, street/flash flooding possible.
Partly to mostly cloudy with isolated showers and isolated thunderstorms favoring the southern half of Trinidad from the early morning, with additional shower/thunderstorm development possible along western coastal Trinidad during the late morning through the afternoon. Elsewhere, partly to mostly cloudy with isolated showers/light to moderate rain. These conditions are forecast to continue into the night. Gusty winds, street/flash flooding possible.
4/10
Thunderstorm Chances
Low – Medium

Tuesday

Tuesday
3 10 0 1
Following isolated early morning showers and thunderstorms mainly in offshore areas, affecting Tobago and eastern coastal Trinidad, a partly cloudy day with isolated afternoon showers favoring western coastal Trinidad. A mostly settled evening, with showers developing across Tobago and eastern Trinidad nearing midnight.
Following isolated early morning showers and thunderstorms mainly in offshore areas, affecting Tobago and eastern coastal Trinidad, a partly cloudy day with isolated afternoon showers favoring western coastal Trinidad. A mostly settled evening, with showers developing across Tobago and eastern Trinidad nearing midnight.
3/10
Thunderstorm Chances
Low

Marine Forecast

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Temperatures

Generally, over the next five days, maximum highs are forecast to be below average due to increased cloud cover while minimum lows remain near to above average.

Tuesday through Saturday

Low: 24-27°C

High: 28-32°C

Maximum high temperatures are forecast to range between 28°C to 32°C trending cooler across eastern Trinidad and higher across urbanized areas of Trinidad, where in built-up areas, maximum high temperatures could exceed 32°C. Minimum lows are forecast to remain warm, ranging between 24°C and 27°C in Trinidad and Tobago, trending cooler in interior areas. The heat index will generally exceed 34°C over the next five days.

Forecast Impacts

Flooding

Flooding
6 10 0 1
Over the next five days, rainfall accumulations will vary between 10 and 55 millimeters across both islands. Isolated totals exceeding 50 millimeters are possible across eastern and southern areas of Trinidad, eastern Tobago and western coastal Trinidad. In highly isolated areas, totals could exceed 100 millimeters over the five-day period in the above-mentioned areas. The heaviest rainfall days are expected on Saturday and Sunday as a result of Tropical Wave 04’s passage.
Over the next five days, rainfall accumulations will vary between 10 and 55 millimeters across both islands. Isolated totals exceeding 50 millimeters are possible across eastern and southern areas of Trinidad, eastern Tobago and western coastal Trinidad. In highly isolated areas, totals could exceed 100 millimeters over the five-day period in the above-mentioned areas. The heaviest rainfall days are expected on Saturday and Sunday as a result of Tropical Wave 04’s passage.
6/10
Likelihood
Medium – High

Forecast Rainfall Totals

  • Friday: Between 0 and 10 millimeters of rainfall across the country, trending higher across eastern Trinidad and Tobago and western coastal Trinidad in localized areas, with isolated totals exceeding 15 millimeters. In areas where thunderstorms develop, totals could exceed 25 millimeters.
  • Saturday: Between 5 and 15 millimeters of rainfall across the country, trending higher across eastern and southern Trinidad, eastern Tobago, and western coastal Trinidad in localized areas, with isolated totals near 25 millimeters. In areas where thunderstorms occur, isolated totals could exceed 25 millimeters.
  • Sunday: Between 5 and 15 millimeters of rainfall across the country, trending higher across Tobago, southern and eastern halves of Trinidad, and western coastal Trinidad with isolated totals near 25 millimeters. In areas where thunderstorms occur, isolated totals could exceed 25 millimeters.
  • Monday: Between 0 and 10 millimeters across both islands, with totals trending higher across the southern half of Trinidad and along western coastal areas, nearing 15 millimeters. In isolated areas, totals could reach 20 millimeters.
  • Tuesday: Less than 5 millimeters of rainfall across most areas of Trinidad, with the exception being eastern coastal areas. Across Eastern Trinidad and Tobago, between 5 and 15 millimeters of rainfall is forecast, with isolated totals of up to 25 millimeters possible.

Putting the rainfall forecast into context, rainfall rates in excess of 50 millimeters per hour or areas that receive in excess of 25 millimeters within an hour tend to trigger street flooding across the country or flash flooding in northern Trinidad. For riverine flooding to occur, a large area of the country (not just in highly localized areas of western coastal Trinidad) would have to record upwards of 75 millimeters within 24 hours, and rainfall would have to fall across major rivers’ catchment areas.

Strong Thunderstorms

Strong Thunderstorms
3 10 0 1
Strong thunderstorms are not likely over the next five days, with only low chances on Saturday as ample moisture, instability and convergence will be present across western and southern areas of Trinidad during the afternoon. Generally moderate to strong wind shear will limit persisting convection.
Strong thunderstorms are not likely over the next five days, with only low chances on Saturday as ample moisture, instability and convergence will be present across western and southern areas of Trinidad during the afternoon. Generally moderate to strong wind shear will limit persisting convection.
3/10
Likelihood
Low

Gusty Winds

Gusty Winds
4 10 0 1
Over the next five days, sustained winds are forecast to be light to gentle, generally remaining below 25 KM/H and gusts up to 40 KM/H possible. In heavy showers or thunderstorms, with higher gusts possible exceeding 45 KM/H, particularly on Saturday and Sunday.
Over the next five days, sustained winds are forecast to be light to gentle, generally remaining below 25 KM/H and gusts up to 40 KM/H possible. In heavy showers or thunderstorms, with higher gusts possible exceeding 45 KM/H, particularly on Saturday and Sunday.
4/10
Likelihood
Low – Medium

Possible impacts include localized wind damage to trees, power lines, and small structures.

Other Hazards

Saharan Dust Forecast

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Why I May Not/Will Not See Rainfall?

A frequent complaint is the forecast is wrong because I didn’t experience any rainfall. Scattered showers mean that you, individually, may experience some showers intermittently throughout the day, and there is a higher chance for this activity than isolated activity. Widespread showers mean that nearly all persons and areas may experience rainfall.

Through the forecast period, isolated to scattered rainfall is forecast, with isolated rainfall forecast on Tuesday.

Forecast Discussion

Tropical Update

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On Friday, the axis of Tropical Wave 04 is forecast to move across Trinidad and Tobago. Ahead of this tropical wave, pockets of low-level convergence in a very moist low to mid-level environment will support some widely scattered showers and isolated heavy pockets and isolated thunderstorms favoring offshore areas.

However, moderate to strong westerly wind shear (between 15-30 knots) is forecast to limit persisting convection (showers and thunderstorms) as it moves west, resulting in relatively short-lived activity. This shear will also keep the heaviest showers and thunderstorms east of T&T and overall higher rainfall totals favoring southern and eastern areas. Additionally, a dry pocket of air is forecast to persist at the mid to upper levels (500mb to 250mb), which will limit deep convection from forming through early Saturday.

By the late morning through the afternoon on Friday, the axis of the wave is forecast to move across the islands, with a favorable low-level convergent environment trailing the wave axis, which will remain across Trinidad and Tobago into the weekend. On a larger scale, this favorable low-level convergent environment stems from T&T and the Windwards being located on the southwestern periphery of a high-pressure system located in the North Atlantic. Additionally, on Friday and particularly on Saturday, upper-level conditions will become marginally favorable, leading to some enhancement of convection.

Based on the latest model guidance, the Intertropical Convergence Zone is forecast to remain just south of Trinidad and Tobago following the passage of Tropical Wave 04 on Saturday through Sunday. However, a weak low-level trough is forecast to develop near/west of Trinidad in the wake of Tropical Wave 04 on Saturday, which will maintain rainfall across the country through the weekend.

Although a high-pressure system regains dominance in the region by Monday, high atmospheric moisture is forecast to remain across Trinidad and Tobago through the remainder of the forecast period. With the ITCZ remaining south of the country, elevated rainfall chances exist for southern Trinidad on Monday. In addition, with winds forecast to slow down next week, daytime heating, sea breeze convergence, and orographic effects (also known as T&T’s local climate effects) will be the dominating triggers for shower and thunderstorm development.

By Tuesday, while the overall total precipitable water remains high, between the 300mb and 850mb (low to upper levels), relative humidity (another measure of atmospheric moisture) is forecast to become increasingly dry, limiting shower and thunderstorm development during the day. By nightfall, however, as Tropical Wave 05’s moisture plume nears, conditions become favorable yet again for shower and thunderstorm development into Wednesday.

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